Monday, June 28, 2010

Bioremediation of Oil Spills - Oxygen requirement

Bioremediation, the Gulf of Mexico oil leak,

In the Gulf of Mexico, bioremediation technologies have come into increased focus as the BP oil leak continues to gush, with up to 7 million barrels of oil now floating in the Gulf after an explosion at an offshore drilling platform in April. According to BioremXL, “bio-remediation transforms the contaminant into food for bacteria that, given the proper conditions, happily consume it. Most bio-remediation products typically become water-logged and sink to the bottom of the lake, stream, ocean, etc. where bacteria cannot grow due to lack of oxygen and sunlight, sometimes having the reverse effect of actually causing even more environmental damage by trapping the oil in an inaccessible place for many years to come.”

UniRem is touting its PRP (Petroleum Remediation Product), which creates miniature spheres comprised of bee’s wax and soy wax to naturally encapsulate oil so that bacteria can consume and transform it into organic matter. These miniature spheres (100 microns in diameter) float at the top of the water where the oil, oxygen, and sun are.


Evan Nyer of Arcadis cautions, “The key to bioremediation of the oil spill is Bacteria, nutrients, and oxygen. There are two schools of thought on the bacteria. One is that someone will make a “super bacteria” that is capable of eating all of the oil in the spill. I am sure that are several companies that are currently offering BP their super bacteria at a reasonable price. My thoughts on bacteria are that they are ubiquitous (everywhere) and that they can double in number every 30 minutes under the right environment conditions. The main things that limit that rate of growth are nutrients (Nitrogen and Phosphorous) and a final electron acceptor (oxygen). So – bacteria are not limiting the rate of bioremediation of the spill.

“Nutrients – during the cleanup efforts in Alaska, studies found that adding nutrients to the shoreline spill areas helped to clean up the oil in those areas. Of course these were in areas that had great wave action which provided the oxygen that the bacteria required. Limited nutrient addition may be able to help the clean up in certain areas.

“Oxygen – this is probably the limiting factor in the rate that the bacteria can eat the oil. The ocean and shore areas have limited ability to transfer oxygen into the water. The maximum oxygen concentration in water is 8 mg/l and we are talking about 100s or 1000s of mg/l of oil contaminant (the dispersants they are using also have to be degraded by the bacteria and add to the oxygen demand of the entire process). So the oxygen must be constantly replenished. This only happens at the air/water interface at the surface of the ocean. Anything that creates surface area and mixing will increase the rate of oxygen transfer. That is why a storm is good news/bad news. It will transfer huge amounts of oxygen, but the waves can help spread the spill. (The sulfate in the ocean can replace the oxygen in the bioremediation, but the bacteria that use sulfate require a very reducing environment and the ocean is not a reducing environment.)

“Tar Balls – In the end the bacteria can only degrade the lower molecular weight compounds from the crude oil. The tar balls cannot use bioremediation.”


Diatoms can provide the oxygen required by bacteria.

Anaerobic bacteria can use sulfur, but deep seas do not support anaerobic bacteria and they are in fact not desirable in deep sea.

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